1. Field of the Invention
The invention relates to a rotor for a rotary electric machine and, particularly, to a rotor for a rotary electric machine which includes a plurality of permanent magnets that are buried in a radially outer-side interior of a rotor iron core, at intervals in the circumferential direction of the rotor iron core.
2. Description of the Related Art
As a related art, a synchronous type rotary electric machine equipped with a rotor 90 that has a magnetic pole construction as shown in FIG. 10 is disclosed in, for example, Japanese Patent Application Publication No. 2009-124899 (JP-A-2009-124899). In this rotor 90, a plurality of magnetic poles 93 (only one magnetic pole is shown in FIG. 10) are provided equidistantly in the circumferential direction within a portion of a cylindrical rotor iron core 91 which is in the vicinity of an outer peripheral surface 92 of the cylindrical rotor iron core 91.
Each magnetic pole 93 has a pair of permanent magnets 94 that are disposed so that the interval distance between the pair of permanent magnets 94 increases toward the outer peripheral surface 92, and a magnetic flux-restraining hole 96 which is formed in a region that is between radially inner end portions 95 of the permanent magnets 94 and that is radially inwardly of the pair of permanent magnets 94. The magnetic flux-restraining hole 96 is constructed of three holes 96a, 96a and 96b. Of the three holes, two end holes 96a and 96a having a generally triangular shape are formed so as to communicate with magnet insertion holes 96, respectively, in which the permanent magnets 94 having an end face shape of a flat elongated rectangle are inserted. Besides, a generally rectangular central hole 96b is formed between the two end holes 96a and 96a, and is separated from the end holes 96a and 96a by bridge portions 97 that are thin iron core regions. It is to be noted herein that radially outer-side (or outer periphery-side) edge portions of the three holes 96a, 96a and 96b are aligned along a straight line 98 shown by a one-dot chain line in FIG. 10 which passes through a radially inner-side corner portion (or edge portion) of each of the pair of permanent magnets 94.
In the rotary electric machine equipped with the rotor 90 whose magnetic poles 93 are constructed as described above, the magnetic flux-restraining hole that includes an air gap at a center of a radially inward portion of each magnetic pole 93 is provided so as to increase the difference between the q-axis inductance Lq and the d-axis inductance Ld of the magnetic pole 93 and therefore enhance the reluctance torque.
In the above-described magnetic poles 93 of the rotor 90 disclosed in Japanese Patent Application Publication No. 2009-124899 (JP-A-2009-124899), a q-axis magnetic path region 99 that is made up of a belt-shaped region having a generally circular arc shape is formed between the pair of permanent magnets 94. Thus, iron core regions 100 that are radially outwardly of the end holes 96a of the magnetic flux-restraining hole 96 (that are above the end holes 96a in FIG. 10) are secured as regions in which no q-axis magnetic flux flows. Besides, since the iron core regions 100 face the radially inner end portions 95 of the permanent magnets 94, the iron core regions 100 allows or causes magnetic fluxes from the radially inner end portions 95 of the magnets 94 to leak or short-circuit toward the bridge portions 97 and the end holes 96a. 